Climate change will not reverse itself.

Long-term average global temperatures have moved in one direction in the past 115 years: upward. The rise of 1.8 degrees Fahrenheit since the start of the Industrial Revolution has already led to more intense wildfire seasons and the melting of Arctic sea ice.

Could those conditions “go back,” as Mr. Trump suggests? In the National Climate Assessment report on science approved by the White House in November, top federal scientists found unequivocally that they will not. The global long-term warming trend is “unambiguous,” they wrote. And as for the idea of natural cycles, they added, “we find no convincing evidence that natural variability can account for the amount of global warming observed over the industrial era.”

The human role

What Mr. Trump said

“I don’t think there’s a hoax. I do think there’s probably a difference. But I don’t know that it’s man-made.”

The facts

Scientists do know that it’s man-made.

The same National Climate Assessment report, vetted by 13 federal agencies, finds “no convincing alternative explanation” that anything other than human activity, particularly the burning of fossil fuels and destruction of forests, is to blame.

NASA embraces the widely cited statistic that “97 percent or more of actively publishing climate scientists agree” that warming trends are the result of human activity, while also listing 200 worldwide scientific organizations that hold to the same findings.

Costs and consequences

“I will say this. I don’t want to give trillions and trillions of dollars. I don’t want to lose millions and millions of jobs. I don’t want to be put at a disadvantage.”

The facts

Not doing anything could cost trillions of dollars.

Here the president is referring in large part to the Paris Agreement, the voluntary pact among nearly 200 nations to curb rising greenhouse gas emissions, from which the Trump administration has vowed to withdraw. In announcing that the United States would abandon the Paris deal, Mr. Trump argued that it would have cost 2.7 million American jobs by 2025 and untold economic revenue.

Science and politics

Asked about scientists who say hurricanes and other extreme weather events are worsening, Mr. Trump replied, “You’d have to show me the scientists because they have a very big political agenda.”

The facts

Scientists dispute that.

No doubt climate change has become politicized. And climate skeptics Sunday night cheered Mr. Trump’s remark. But scientists took umbrage at the notion that their research has an agenda. Here are three in their own words:

Katharine Hayhoe, climate scientist, Texas Tech University: “A thermometer isn’t Democrat or Republican. It doesn’t give us a different answer depending on how we vote.”

Andrew Dessler, climate scientist, Texas A&M University: “At its heart, this is just a wacky conspiracy theory,” he wrote. “It’s important to realize that there’s never been a conspiracy by a huge field of science. And this would have to be an extremely massive conspiracy, considering the thousands of scientists working on this. On the other hand, there have been many examples (cigarettes, anyone?) where political advocates have tried to cast doubt on science that is extremely solid. That’s what’s going on here.”

Donald Wuebbles, climate scientist, University of Illinois: “No scientists have political agendas. That’s just an excuse.”

What others said

Larry Kudlow, the president’s top economic adviser, and Senator Marco Rubio, Republican of Florida, also distanced themselves on Sunday from the I.P.C.C. report. Both made claims similar to Mr. Trump’s about a supposed disagreement among scientists about the role of human activity in climate change.

For more on climate change, how we know it’s happening and how we know humans are responsible, read our Q. and A. here: